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Abstract:

In an attachment control apparatus for a hydraulic excavator having a
hydraulic circuit that includes a hydraulic pump, a plurality of
actuators having a breaker which is an attachment actuator, and a
plurality of flow control valves having an attachment flow control valve
that is switched by operation pilot pressure from a control pedal device
to supply delivery fluid of the hydraulic pump to the attachment
actuator, if the control pedal device is operated in a state where an
attachment mode is not selected by an attachment selection device, the
movement of the attachment actuator is limited. Thus, failure and reduced
life of the attachment and other hydraulic devices can be prevented in
the event that an operator has forgotten to switch from a normal mode to
an attachment mode and has operated the attachment.

Claims:

1. An attachment control apparatus for a hydraulic excavator having a
hydraulic circuit that includes at least one hydraulic pump, a plurality
of actuators having an attachment actuator, and a plurality of flow
control valves having an attachment flow control valve that is switched
by operation pilot pressure from attachment operating means to supply
delivery fluid of the hydraulic pump to the attachment actuator, the
attachment control apparatus comprising: mode switching means for
selecting either a non-attachment mode or an attachment mode and, upon
selection of the attachment mode, switching a state of the hydraulic
circuit to a state suitable for operating the attachment actuator; and
movement limiting means for limiting the movement of the attachment
actuator when the attachment operating means is operated in a state where
the attachment mode is not selected by the mode switching means.

2. The attachment control apparatus for the hydraulic excavator according
to claim 1, wherein the movement limiting means limits the flow rate of
hydraulic fluid that is supplied to the attachment actuator, thereby
limiting the movement of the attachment actuator.

3. The attachment control apparatus for the hydraulic excavator according
to claim 2, wherein the movement limiting means limits the delivery rate
of the hydraulic pump, thereby limiting the flow rate of the hydraulic
fluid that is supplied to the attachment actuator.

4. The attachment control apparatus for the hydraulic excavator according
to claim 2, wherein the movement limiting means limits the flow rate of
hydraulic fluid passing through the attachment flow control valve,
thereby limiting the flow rate of the hydraulic fluid that is supplied to
the attachment actuator.

Description:

TECHNICAL FIELD

[0001] The present invention relates generally to an attachment control
apparatus for a hydraulic excavator. The invention particularly relates
to an attachment control apparatus for a hydraulic excavator having a
hydraulic circuit for an attachment mounted on a front work device of the
hydraulic excavator.

BACKGROUND ART

[0002] A construction machine or a hydraulic excavator excavates and
performs other works using a versatile bucket mounted on the leading end
of a front work device. In addition, a construction machine or a
hydraulic excavator excavates and performs various works with the use of
an attachment such as a breaker, a crusher or the like in place of using
the versatile bucket.

[0003] For attachments mounted on the front work device, specifications
covering pressure, flow rate, etc. of hydraulic fluid are defined
according to the type of each attachment. It is necessary, therefore, to
change the setting of a hydraulic circuit or the like depending on the
type of an attachment mounted on the front work device.

[0004] Conventional technologies for changing the setting (the mode)
according to the type of the attachment mounted on the front work device
are disclosed in, for example, Patent Documents 1 and 2.

[0005] The conventional technology described in Patent Document 1 is as
below. A connector is attached to an attachment such as a breaker or the
like. This connector sets bit patterns specific to respective attachments
according the presence or absence of grounding of a plurality of cables.
The connector is connected via a harness to a control unit installed on a
construction machine main body side. Upon detection of the operation of
the attachment, a hydraulic pump is controlled by use of a control
condition set value corresponding to the bit pattern specific to the
attachment, among the pump control condition set values stored previously
in the control unit. In this way, a pump control condition suitable for a
particular attachment can be set from among the pump control conditions
required for a plurality of the attachments.

[0006] The conventional technology described in Patent Document 2 is as
below. If a low-capacity type actuator is mounted that does not need the
maximum amount of fluid from a hydraulic pump, an operator switches a
mode-changeover switch to a low-capacity type actuator use mode.
Concurrently, the operator uses an accelerator potentiometer as a maximum
delivery rate setting means to set the upper limit of hydraulic fluid
delivery rate. The operator then selects minimum delivery rate from among
the following: the hydraulic fluid delivery rate set by the maximum
delivery rate setting means; a hydraulic fluid delivery rate
positive-controlled in response to the operation amount of an operating
pedal; and a hydraulic fluid delivery rate resulting from P-Q control in
which the maximum torque of the hydraulic pump is set so as not to
provide an excessive load to thereby limit the pump delivery rate. Thus,
the flow rate of the hydraulic fluid delivered from the hydraulic pump is
tilting-controlled such that hydraulic fluid is delivered at the selected
delivery rate.

[0009] However, the above-mentioned technologies do not consider the
problem encountered when the operator forgets to switch from the normal
mode to the attachment mode. The attachment may be operated still in the
normal mode where the setting corresponding to the type of the attachment
is not done. In such a case, the attachment is used with its
specifications exceeded consequently, so that there is concern about the
failure and reduced life of the attachment and of the other hydraulic
devices. In addition, foreign matter such as dust or the like gets mixed
in with return oil in some cases. An attachment such as a breaker or the
like in which it is desired to directly return a return oil to a tank not
via a control valve may be used still in the normal mode where the return
oil should be returned to the tank via the control valve. In such a case,
spool stick or the like due to dust or the like may possibly occur. As
with the case where the attachment has been used with its specifications
exceeded, there is concern about the occurrence of the failure and
reduced life of the attachment and of the other hydraulic devices.

[0010] The present invention has been made in view of the above and aims
to provide an attachment control apparatus for a hydraulic excavator that
can prevent the failure and reduced life of an attachment and of other
hydraulic devices in the event that an operator has forgotten to switch
from a normal mode to an attachment mode and has operated the attachment.

Means for Solving the Problem

[0011] (1) To achieve the above object, in the present invention, there is
provided an attachment control apparatus for a hydraulic excavator having
a hydraulic circuit that includes at least one hydraulic pump, a
plurality of actuators having an attachment actuator, and a plurality of
flow control valves having an attachment flow control valve that is
switched by operation pilot pressure from attachment operating means to
supply delivery fluid of the hydraulic pump to the attachment actuator.
The attachment control apparatus includes: mode switching means for
selecting either a non-attachment mode or an attachment mode and, upon
selection of the attachment mode, switching a state of the hydraulic
circuit to a state suitable for operating the attachment actuator; and
movement limiting means for limiting the movement of the attachment
actuator when the attachment operating means is operated in a state where
the attachment mode is not selected by the mode switching means.

[0012] As described above, if the attachment operating means is operated
in the state where the attachment mode is not selected, the movement of
the attachment actuator is limited. Because of this constitution, in the
event that the operator has forgotten to switch from the non-attachment
mode to the attachment mode and has operated the attachment, it is
possible to allow the operator to recognize the forgetting of the
switching between the modes, and to prompt the operator to switch the
mode to the attachment mode. Thus, it is possible to prevent the failure
and reduced life of the attachment and of the other hydraulic devices.

[0013] (2) In the above (1), the movement limiting means limits the flow
rate of hydraulic fluid that is supplied to the attachment actuator,
thereby limiting the movement of the attachment actuator.

[0014] With this, if the attachment operating means is operated in the
state where the attachment mode is not selected, the amount of fluid to
be supplied to the attachment actuator is limited. Therefore, in the
event that the operator has forgotten to switch from the non-attachment
mode to the attachment mode and has operated the attachment, it is
possible to allow the operator to recognize the forgetting of the
switching between the modes, and to prompt the operator to switch the
mode to the attachment mode. In addition, it is possible to suppress the
use of the attachment with its specifications exceeded. Thus, it is
possible to prevent the failure and reduced life of the attachment and of
the other hydraulic devices.

[0015] (3) In the above (2), the movement limiting means limits the
delivery rate of the hydraulic pump, thereby limiting the flow rate of
the hydraulic fluid that is supplied to the attachment actuator.

[0016] (4) In the above (2), the movement limiting means limits the flow
rate of hydraulic fluid passing through the attachment flow control
valve, thereby limiting the flow rate of the hydraulic fluid that is
supplied to the attachment actuator.

Effect of the Invention

[0017] The present invention can prevent the failure and reduced life of
the attachment and of the other hydraulic devices in the event that the
operator has forgotten to switch from the normal mode to the attachment
mode and has operated the attachment.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 schematically illustrates the entire configuration of a
hydraulic circuit system for a hydraulic excavator provided with an
attachment control apparatus according to a first embodiment of the
present invention.

[0019]FIG. 2 is a block diagram illustrating processing contents of a
control unit according to the first embodiment of the present invention.

[0020]FIG. 3 illustrates the details of processing contents of a pump
capacity control section according to the first embodiment of the present
invention.

[0021]FIG. 4 illustrates the details of processing contents of a
hydraulic line control section according to the first embodiment of the
present invention.

[0022]FIG. 5 illustrates the external appearance of the hydraulic
excavator to which the attachment control apparatus according to the
first embodiment of the present invention is applied.

[0023] FIG. 6 schematically illustrates the entire configuration of a
hydraulic circuit system for a hydraulic excavator provided with an
attachment control apparatus according to a second embodiment of the
present invention.

[0024] FIG. 7 is a block diagram illustrating processing contents of a
control unit according to the second embodiment of the present invention.

[0025] FIG. 8 illustrates the details of processing contents of a pump
capacity control section according to the second embodiment of the
present invention.

[0026]FIG. 9 illustrates the details of processing contents of a pilot
pressure control section according to the second embodiment of the
present invention.

MODE FOR CARRYING OUT THE INVENTION

[0027] Embodiments of the present invention will hereinafter be described
with reference to the drawings.

First Embodiment

[0028] FIG. 1 schematically illustrates the entire configuration of a
hydraulic circuit system for a hydraulic excavator provided with an
attachment control apparatus according to a first embodiment of the
present invention.

[0029] Referring to FIG. 1, the hydraulic circuit system for the hydraulic
excavator includes a prime mover 1 such as an engine; two main pumps,
i.e., variable displacement first and second hydraulic pumps 2 and 3
driven by the prime mover 1; a fixed displacement pilot pump 4 driven by
the prime mover 1; a control valve unit 5 connected to the first and
second hydraulic pumps 2, 3; a breaker 110 as an attachment connected to
the control valve unit 5; a plurality of hydraulic actuators (see
subsequent FIG. 5) including a boom cylinder 111, an arm cylinder 112, a
bucket cylinder 113 and a swing motor 107 which are connected to the
control valve unit 5 and not shown in the figure; a control pedal device
7 (attachment operating means) for operating the attachment (the breaker
110 in the embodiment); a plurality of operating units (not shown)
including the operating units (not shown) for operating hydraulic
actuators such as the boom cylinder 111, the arm cylinder 112, the bucket
cylinder 113, the swing motor 107, traveling motors 114a, 114b, etc.; and
pump capacity control systems 8, 9 for controlling the capacities
(displacement volume or tilting of a swash plate) of the first and second
hydraulic pumps 2, 3.

[0030] An attachment is mounted on a front work device 103 (see subsequent
FIG. 5) in place of the bucket used for excavating, etc. and is used for
various works. In the present embodiment, a description is given taking
as an example the case where the breaker 110, one of attachments, is
mounted on the front work device 103. The breaker 110, one of the
attachments, is mounted on the leading end of the front work device 103
and used for performing work for crushing a massive object such as a
large rock, a concrete mass or the like. The breaker 110 includes a
hitting rod 110a composed of a steel rod having a point, or the like; and
a breaker cylinder 110b used to drive the hitting rod 110a. The breaker
110 is designed such that hydraulic fluid is fed to a supply port (not
shown) of the breaker cylinder 110b to allow the hitting rod 110a to
reciprocate for hitting the massive object for fracture.

[0031] The control valve unit 5 has first and second valve groups 5a and
5b corresponding to the first and second hydraulic pumps 2 and 3,
respectively. The first valve group 5a has a plurality of flow control
valves A1 to A4 and the second valve group 5b has a plurality of flow
control valves B1 to B5.

[0032] In the first valve group 5a, the flow control valves A1 to A4 are
center bypass type flow control valves arranged on a center bypass line
10 connected to a delivery line 2a of the first hydraulic pump 2 in the
order of the flow control valves A1 to A4 from the upstream side. In the
second valve group 5b, the flow control valves B1 to B5 are center bypass
type flow control valves arranged on a center bypass line 11 connected to
a delivery line 3a of the second hydraulic pump 3 in the order of the
flow control valves B1 to B5 from the upstream side. In the first and
second valve groups 5a, 5b, the respective most downstream sides of the
center bypass lines 10, 11 are connected to a tank T. When the flow
control valves A1 to A4, B1 to B4 are each at a neutral position shown in
the figure, the respective delivery lines 2a, 3a of the first and second
hydraulic pumps 2, 3 communicate with the tank T via the corresponding
center bypass lines 10, 11 so that the delivery pressure of each of the
first and second hydraulic pumps 2, 3 lowers to a tank pressure.

[0033] The flow control valve B4 is used for driving the attachment. In
the embodiment, the flow control valve B4 has two actuator ports, one of
which is connected to a supply port (not sown) of the breaker 110, the
attachment, via a first actuator line 61. The other is connected to a
discharge port (not shown) of the breaker 110 via a second actuator line
62. The second actuator line 62 is composed of two portions, i.e.,
hydraulic lines 62a, 62b. The flow control valve B4 has first and second
pressure-receiving portions 51a, 51b. If operation pilot pressure is led
to the first pressure-receiving portion 51a, the flow control valve B4 is
switched to a right position in the figure to supply the delivery fluid
of the second hydraulic pump 3 to the attachment via the first actuator
line 61. If the operation pilot pressure is led to the second
pressure-receiving portion 51b, the flow control valve B4 is switched to
a left position in the figure to supply the delivery fluid of the second
hydraulic pump 3 to the attachment via the second actuator line 62.
However, in the breaker 110, i.e., the attachment used in the embodiment,
the supply port and the discharge port for hydraulic fluid are fixed.
Therefore, the position of the flow control valve B4 is switched to only
the right position in the figure where the delivery fluid of the second
hydraulic pump 3 is supplied to the supply port of the breaker 110 via
the first actuator line 61. Relief valves 63 and 64 are respectively
connected to the first and second actuator lines 61 and 62 connected to
the two actuator ports of the flow control valve B4. In this way, the
pressure of the hydraulic fluid flowing in the first and second actuator
lines 61, 62 is regulated to a given level or below.

[0034] Although illustration and detailed description are omitted, the
flow control valves A1 to A4 of the first valve group 5a and the flow
control valves B1 to B3, B5 of the second valve group 5b are used for
driving the plurality of hydraulic actuators (not shown) including the
boom cylinder 111, the arm cylinder 112, the bucket cylinder 113 and the
swing motor 107 (see subsequent FIG. 5). Also these flow control valves
have pressure-receiving portions similarly to the flow control valve B4
and are each operatively switched similarly thereto.

[0035] The control valve unit 5 is provided with a main relief valve 17.
The relief valve 17 is connected to the respective delivery lines 2a and
3a of the first and second hydraulic pumps 2, 3 via non-return valves
(check valves) 18 and 19, respectively. The relief valve 17 is adapted to
regulate the delivery pressure of each of the first and second pumps 2, 3
to a given level or below. The check valves 18, 19 are connected in
parallel to the input port side of the main relief valve 17. In addition,
the check valves 18, 19 permit hydraulic fluid to flow from the first and
second pumps 2, 3 toward the main relief valve 17 but inhibit it from
flowing in the reverse direction. A pilot relief valve 16 is connected to
a delivery line 4a of the pilot pump 4. The pilot relief valve 16 is
adapted to maintain the delivery pressure of the pilot pump 4 at a
constant level.

[0036] The pump capacity control system 8 is adapted to control the
capacity (displacement volume or tilting of a swash plate) of the first
hydraulic pump 2 which supplies hydraulic fluid to the actuators
corresponding to the first valve group 5a. The pump capacity control
system 8 controls the capacity of the first hydraulic pump 2 on the basis
of operation signals (operation pilot pressures) or the like of operating
units associated with the flow control valves A1 to A4 of the first valve
group 5a.

[0037] The pump capacity control system 9 is adapted to control the
capacity of the second hydraulic pump 3 which supplies hydraulic fluid to
the actuators corresponding to the second valve group 5b that is a valve
group including the flow control valve B4 limiting the flow rate of the
hydraulic fluid supplied to the actuator. The pump capacity control
system 9 controls the capacity of the second hydraulic pump 3 on the
basis of pilot pressure selected by a shuttle valve group 21 to be
described later and led via a pilot line 21a, among operation signals
(operation pilot pressures) of operating units (not shown) associated
with the flow control valves B1 to B5 of the second valve group 5b, such
as the control pedal device 7 (to be described later) which is an
operating unit associated with the flow control valve B4.

[0038] The control pedal device 7 (the attachment operating means) is of a
hydraulic pilot type having a control pedal 7c. In addition, the control
pedal device 7 outputs operation pilot pressure as an attachment
operating signal in response to the operating direction and operation
amount of the control pedal 7c. The operation pilot pressure outputted
from the control pedal device 7 is led via pilot lines 7a and 7b to the
corresponding pressure-receiving portions 51a and 51b, respectively, of
the flow control valve B4 for driving the attachment. A shuttle valve 7f
connected between the pilot lines 7a and 7b selects the higher of
operation pilot pressures outputted to the pilot lines 7a, 7b, i.e., the
pilot pressure corresponding to the operation amount of the control pedal
7c. Such pilot pressure is led to the shuttle valve group 21 to be
described later via a pilot line 7d.

[0039] The shuttle valve group 21 is connected to the pilot line 7d from
the control pedal device 7. In addition, the shuttle valve 21 is
connected to each of pilot lines (not shown) adapted to lead operation
pilot pressure to a corresponding one of the flow control valves B1 to B5
of the second valve group 5b from a corresponding one of operating units
(not shown) for operating hydraulic actuators such as the boom cylinder
111, the arm cylinder 112, the bucket cylinder 113, the swing motor 107,
the traveling motors 114a, 114b, etc.

[0040] The shuttle valve group 21 has a shuttle valve 21b and a plurality
of shuttle valves not shown. The shuttle valves not shown are provided to
connect together the pilot lines of the plurality of operating units not
shown in a tournament manner to extract the maximum pressure of the pilot
pressures in the pilot lines. In addition, the shuttle valve 21b is
connected between the pilot line 7b and an output port of the final-stage
shuttle valve associated with another operating unit not shown. In this
way, the shuttle valve group 21 having the shuttle valve 21b as the final
stage extracts and outputs the maximum pressure among the operation pilot
pressures from the control pedal device 7 and the operation pilot
pressures from the other operating units not shown. The output port of
the final-stage shuttle valve 21b is connected to the pump capacity
control system 9 of the second hydraulic pump 3 via the pilot line 21a.
The capacity of the second hydraulic pump 3 is controlled based on the
operating conditions of the control pedal device 7 and of the other
operating units.

[0041] An attachment control apparatus according to the present embodiment
is installed in such a hydraulic circuit system for a hydraulic
excavator. The attachment control apparatus includes an attachment
selection device 20 (mode switching means), an operation amount sensor 7e
installed in the control pedal device 7, a solenoid proportional valve
13, a solenoid directional control valve 14, a directional control valve
15 and a control unit 12.

[0042] The attachment selection device 20 is used by an operator to select
an operation mode in accordance with the bucket or the type of the
attachment which are mounted on the front work device 103 of the
hydraulic excavator. The attachment selection device 20 has a rotating
dial 20a for selecting the operation mode. The rotating dial 20a is
designed to be capable of not only rotating operation but also
depression. The operation mode is selected by the combination of the
rotating operation with depressing operation of the rotating dial 20a.
For example, if the operation mode is to be switched to ATT1, the
position of operation mode name ATT1 is selected with the rotating dial
20a as shown in FIG. 1 and the rotating dial 20a is depressed. The
selection result of the attachment selection device 20 is sent to the
control unit 12.

[0043] The operation amount sensor 7e is adapted to detect an operation
amount of the control pedal 7c of the control pedal device 7 used to
operate the attachment and sends the detection result (the operation
amount of the control pedal 7c) to the control unit 12.

[0044] The solenoid proportional valve 13 is installed on the pilot line
21a connecting the final-stage shuttle valve 21b of the shuttle valve
group 21 with the pump capacity control system 9 of the second hydraulic
pump 3. The solenoid proportional valve 13 regulates the pilot pressure
led from the shuttle valve group 21 to the pump capacity control system 9
in accordance with a control current flowing from the control unit 12 to
a solenoid 13b. When the current flowing from the controller 12 to the
solenoid 13b is equal to 0, the solenoid proportional valve 13 is
switched to the right position shown in the figure by the force of a
spring 13c. As the current flowing to the solenoid 13b is increased, the
solenoid proportional valve 13 is gradually switched to the left position
shown in the figure to reduce the pilot pressure led to the pump capacity
control system 9.

[0045] The solenoid directional control valve 14 is connected to a pilot
line 14a that is connected to a pressure-receiving portion 15a of the
directional control valve 15. The solenoid directional control valve 14
is ON/OFF controlled in accordance with the current flowing from the
control unit 12 to a solenoid 14b. When the current flowing from the
controller 12 to the solenoid 14b is equal to 0, the solenoid directional
control valve 14 is switched to the left position (the OFF-position)
shown in the figure by the force of a spring 14c. The pilot line 14a
communicates with the delivery line 4a of the pilot pump 4. The pilot
pressure of the pilot line 4a is supplied to the pressure-receiving
portion 15a of the directional control valve 15 to be described later.
When an excitation current is allowed to flow from the controller 12 to
the solenoid 14b, the solenoid directional control valve 14 is switched
to the right position (the ON-position) shown in the figure. The pilot
line 14a communicates with the tank T so that the pressure-receiving
portion 15a of the directional control valve 15 is at a tank pressure.

[0046] The directional control valve 15 is installed between the hydraulic
lines 62a and 62b of the second actuator line 62 that is connected to the
discharge port of the breaker 110 which is an attachment. The directional
control valve 15 is ON/OFF controlled in accordance with the pilot
pressure led to the pressure-receiving portion 15a via the pilot line
14a. When the pilot pressure to be led to the pressure-receiving portion
15a is at a tank pressure, the directional control valve 15 is switched
by the force of a spring 15b to the right position shown in the figure at
which the hydraulic line 62a is communicated with the hydraulic line 62b.
When the pilot pressure to be led to the pressure-receiving portion 15a
is at the delivery pressure of the pilot pump 4, the directional control
valve 15 is switched to the left position shown in the figure at which
the hydraulic line 62a is communicated with the tank T. That is, when the
directional control valve 15 is at the left position shown in the figure,
the discharge port of the breaker 110 which is an attachment is connected
via the hydraulic line 62a to the tank T, so that the return oil from the
breaker 110 is directly led to the tank T.

[0047] The control unit 12 controls the attachment control apparatus
according to the present embodiment. The control unit 12 sends current to
the solenoid proportional valve 13 and the solenoid directional control
valve 14 on the basis of the input from the attachment selection device
20 and the operation amount sensor 7e.

[0048]FIG. 2 is a block diagram illustrating processing contents of the
control unit according to the present embodiment. FIG. 3 illustrates the
details of processing contents of a pump capacity control section. FIG. 4
illustrates the details of processing contents of a hydraulic line
control section. Incidentally, FIGS. 2 to 4 concurrently illustrate the
attachment selection device 20 for explanation.

[0049] Referring to FIG. 2, the control unit 12 includes a capacity
control section 12A (see FIG. 3) and a hydraulic line control section 12B
(see FIG. 4). The capacity control section 12A controls the capacity of
the second hydraulic pump 3 by controlling the solenoid proportional
valve 13 on the basis of the selection result of the attachment selection
device 20 and the detection result of the operation amount sensor 7e of
the control pedal device 7. The hydraulic line control section 12B
switches between the positions of the directional control valve 15 by
controlling the solenoid directional control valve 14 on the basis of the
selection result of the attachment selection device 20.

[0051] The pump upper-limit capacity first calculation section 70 receives
the detection result of an operation amount of the control pedal 7c from
the operation amount sensor 7e of the control pedal device 7, i.e. the
detection result of the attachment operation amount (the ATT operation
amount). The first calculation section 70 then refers the detection
result to a table stored in a memory and calculates a pump upper-limit
capacity corresponding to the then ATT operation amount. In the table of
the memory, the relationship between the ATT operation amount and the
pump upper-limit capacity is established as below. When the ATT operation
amount is small, the pump upper-limit capacity is large (e.g. the maximum
delivery capacity of the second hydraulic pump 3). As the ATT operation
amount is increased, the pump upper-limit capacity is gradually reduced.
The pump upper-limit capacity is reduced to a level (for example, the
delivery capacity of a minimal value capable of containing the whole of
the setting values of pump upper-limit flow set in pump upper-limit flow
setting sections 71b to 71i of the pump upper-limit flow setting section
group 71 to be described later) where the delivery rate of the second
hydraulic pump 3 is a basic flow rate. In other words, when the control
pedal 7c of the control pedal device 7 (the attachment operating means)
is not operated or the operation amount is small, the maximum delivery
capacity is set as a pump upper-limit capacity so as not to limit the
upper-limit flow of the second hydraulic pump 3. When the control pedal
7c is operated at a maximum, the maximum delivery capacity is set at the
above-mentioned pump upper-limit capacity (the pump upper-limit capacity
where the delivery rate of the second hydraulic pump 3 is a basic flow
rate). With the exception of the above, the pump upper-limit capacity is
set so as to have metering (a flow-rate change characteristic) in view of
maneuverability.

[0052] The pump upper-limit flow setting section group 71 has the
plurality of pump upper-limit flow setting sections 71b to 71i setting
respective pump upper-limit flow rates suitable to perform excavating
using a bucket or various works using various corresponding attachments.
The pump upper-limit flow setting sections 71b to 71i set therein the
respective pump upper-limit flows of the second hydraulic pump 3 suitable
to perform various works by mounting various corresponding attachments
(ATT) to the front work device 103. In the present embodiment, the
breaker 110 is set as ATT1. The ATT1 upper-limit flow setting section 71b
sets therein a pump upper-limit flow rate of the second hydraulic pump 3
suitable for the case where the breaker 110 is mounted to the front work
device 103 for crushing work. This holds true for the other pump
upper-limit flow setting sections 71c to 71i. Various attachments are set
as ATT2 to ATT8. The pump upper-limit flow setting sections 71c to 71i
set therein the pump upper-limit flows of the second hydraulic pump 3
each corresponding to the type of the attachment.

[0053] The pump upper-limit flow selection switch section 72 is switched
to a position corresponding to an operation mode selected by the
attachment selection device 20. In addition, the pump upper-limit flow
selection switch section 72 outputs, to the division section 74, a pump
upper-limit flow rate corresponding to excavation work with a bucket
selected by the attachment selection device 20 or to each attachment,
among the pump upper-limit flow rates set by the pump upper-limit flow
setting sections 71b to 71i of the pump upper-limit flow setting section
group 71. FIG. 2 illustrates the case as below. The attachment selection
device 20 selects ATT1 (the breaker) so that the pump upper-limit flow
selection switch section 72 is switched to the upper-limit flow setting
section 71b corresponding to ATT1. In this way, the pump upper-limit flow
selection switch section 72 outputs, to the division section 74, the pump
upper-limit flow rate set in the pump upper-limit flow setting section
71b, i.e., the pump upper-limit flow rate of the second hydraulic pump 3
suitable for the case where the breaker 110 is mounted as an attachment
to the front work device 103 for performing crushing work.

[0054] The target engine-speed setting section 73 sets therein a target
engine-speed preset by an engine speed control dial or the like not
shown.

[0055] The division section 74 divides a pump upper-limit flow rate
selected and set by the pump upper-limit flow selection switch section
72, by the target engine-speed set by the target engine-speed setting
section 73. In addition, the division section 74 outputs the divided
value to the maximum value selection section 75.

[0056] The maximum value selection section 75 selects the maximum value of
the pump upper-limit capacity calculated by the pump upper-limit capacity
first calculation section 70 and the calculation result of the division
section 74, and outputs it to the operation mode selection switch section
77.

[0057] The pump upper-limit capacity second calculation section 76
receives the detection result of the operation amount (the ATT operation
amount) of the control pedal 7c from the operation amount sensor 7e of
the control pedal device 7. Then, the second calculation section 76
refers the detection result to a table stored in a memory and calculates
the pump upper-limit capacity corresponding to the then ATT operation
amount. In the table of the memory, the relationship between the ATT
operation amount and the pump upper-limit capacity is established as
below. If the ATT operation amount is equal to 0 (zero) or is so small as
to be regarded as 0 (zero), the pump upper-limit capacity is large (e.g.
the maximum delivery capacity of the second hydraulic pump 3). If the ATT
operation amount is increased (i.e., if the control pedal 7c is
operated), the pump upper-limit capacity is reduced at once to a level
where the delivery rate of the second hydraulic pump 3 is a basic flow
rate.

[0058] If the attachment selection device 20 selects the mode in which an
attachment is used (attachment mode: ATT1 to ATT8), the operation mode
selection switch section 77 is switched to an attachment mode (ATT mode)
side. In addition, the operation mode selection switch section 77 selects
the pump capacity calculated by the maximum value selection section 75
and outputs it to the proportional valve pressure calculation section 78.
If the attachment selection device 20 selects the mode in which
excavation is performed by use of the bucket (non-attachment mode:
excavation), the operation mode selection switch section 77 is switched
to the side except the ATT mode. In addition, the operation mode
selection switch section 77 selects the pump capacity calculated by the
pump upper-limit capacity second calculation section 76 and outputs it to
the proportional valve pressure calculation section 78.

[0059] The proportional valve pressure calculation section 78 receives the
pump capacity selected by the operation mode selection switch section 77
and refers it to a table stored in a memory. In addition, the
proportional valve pressure calculation section 78 calculates
proportional valve pressure corresponding to the then pump capacity. In
the table of the memory, the relationship between the pump capacity and
the proportional valve pressure is established such that as the pump
capacity is increased, the proportional valve pressure is gradually
increased.

[0060] The proportional valve output current calculation section 79
receives the proportional valve pressure calculated by the proportional
valve pressure calculation section 78 and refers it to a table stored in
a memory. In addition, the proportional valve output current calculation
section 79 calculates a proportional valve output current corresponding
to the then proportional valve pressure. In the table of the memory, the
relationship between the proportional valve pressure and the proportional
valve output current is established such that as the proportional valve
pressure is increased, the proportional valve output current is gradually
reduced. The proportional valve output current calculated by the
proportional valve output current calculation section 79 is output to the
solenoid 13b of the solenoid proportional valve 13.

[0061] Referring to FIG. 4, the hydraulic line control section 12B has a
function of each of a solenoid valve OFF-setting section 80, a solenoid
valve ON-setting section 81, and an attachment selection switch section
82.

[0062] The solenoid valve OFF-setting section 80 has a function of
outputting a current (current 0 (zero)) adapted to OFF-control the
solenoid valve 14. The solenoid valve ON-setting section 81 has a
function of outputting a current adapted to ON-control the solenoid valve
14, i.e., to energize the solenoid 14b of the solenoid valve 14 to switch
the solenoid valve 14 to an ON-position.

[0063] If the attachment selection device 20 selects the mode (ATT1) in
which the breaker 110 is used as an attachment, the attachment selection
switch section 82 is switched to a solenoid valve OFF-setting section 80
side. In addition, the attachment selection switch section 82 outputs a
current adapted to OFF-control the solenoid valve 14 (to switch it to the
OFF-position), as the output of the hydraulic line control section 12B.
If the attachment selection device 20 selects the mode (excavation, or
any one of ATT2 to ATT8) except ATT1, the attachment selection switch
section 82 is switched to a solenoid valve ON-setting section 81 side. In
addition, the attachment selection switch section 82 outputs a current
adapted to ON-control the solenoid valve 14 (to switch it to the
ON-position), as the output of the hydraulic line control section 12B.

[0064]FIG. 5 illustrates the external appearance of the hydraulic
excavator to which the attachment control apparatus according to the
embodiment is applied. In addition, FIG. 5 illustrates the case where the
breaker 110, one of attachments, is mounted.

[0065] Referring to FIG. 5, the hydraulic excavator includes a lower
travel structure 100; an upper swing structure 101 mounted swingably on
the upper portion of the lower travel structure 100; the front work
device 103 coupled to the leading end portion of the upper swing
structure 101 via a swing post 102 so as to be swingable vertically and
horizontally; and an earth removal blade 104 installed vertically movably
on the front side of the lower travel structure 100. An engine room 105
and a cabin 106 are installed on the upper swing structure 101. The swing
motor 107 is installed on the upper swing structure 101. Thereby, the
upper swing structure 101 is swingably driven by the rotation of the
swing motor 107. The front work device 103 includes a boom 108 connected
to the swing post 102 vertically swingably; an arm 109 connected to the
leading end of the boom 108 vertically swingably; and the breaker 110 as
an attachment connected to the leading end of the arm 109 so as to be
swingable in the back and forth direction. The boom 108, the arm 109 and
the breaker 110 are swingably driven by the boom hydraulic cylinder 111,
the arm hydraulic cylinder 112 and a bucket hydraulic cylinder 113,
respectively. The lower travel structure 100 is provided with left and
right traveling motors 114a, 114b (only one is shown) and is driven by
the rotation of the traveling motors 114a, 114b.

[0066] Incidentally, FIG. 1 omits the illustrations of actuators other
than that of the breaker 110 (the attachment) shown in FIG. 3, namely,
the actuators such as the traveling motors 114a, 114b and the like, and
flow control valves corresponding thereto.

[0067] The control pedal device 7 shown in FIG. 1 is disposed inside the
cabin 106. The engine 1, the first and second hydraulic pumps 2, 3 and
the pilot pump 4 are disposed inside the engine room 105. The hydraulic
devices such as the control valve unit 5 and the like are disposed in
position on the upper swing structure 101.

[0068] A description is given of the operation in the embodiment
configured as described above.

(1) At the Time of Selecting the Non-Attachment Mode

[0069] If the attachment selection device 20 selects the excavation mode
(the non-attachment mode), the pump upper-limit flow selection switch
section 72 is switched to one (e.g. the ATT1 pump upper-limit flow
setting section 71b) of the pump upper-limit flow setting section group
71. In addition, the operation mode selection switch section 77 is
switched to the side except the ATT mode. The proportional valve pressure
calculation section 78 calculates proportional valve pressure by use of
the pump upper-limit capacity calculated by the pump upper-limit capacity
second calculation section 76. The pump proportional valve output
calculated by the proportional valve output current calculation section
79 by use of the proportional valve pressure becomes the output of the
control unit 12. Additionally, the attachment selection switch section 82
is switched to the solenoid valve ON-setting section 81 side. The
solenoid directional control valve output adapted to ON-control the
solenoid directional control valve 14 becomes the output of the control
unit 12. If the solenoid directional control valve 14 is ON-controlled,
the pilot line 14a is at a tank pressure. The directional control valve
15 is switched to the right position shown in the figure, so that the
hydraulic lines 62a, 62b of the second actuator line 62 are allowed to
communicate with each other.

(1-1) In the Case where the Operating Unit Corresponding to the Front
Work Device 103 is Operated

[0070] If the operating units (not shown) of the actuators corresponding
to the flow control valves B1 to B5 of the second valve group 5b are
operated, the maximum pressure among their operation signals (the
operation pilot pressures) is extracted by the shuttle valve group 21 and
led to the capacity control system 9. The capacity control system 9
controls the capacity of the second hydraulic pump 3 on the basis of such
a pilot pressure. In other words, the capacity of the second hydraulic
pump 3 is controlled so that the amount of fluid necessary to be supplied
to the corresponding actuators via the flow control valves B1 to B5 of
the second valve group 5b is delivered. In this way, the bucket is
mounded on the front work device 103 and excavating can be done.

(1-2) In the Case where the Control Pedal Device 7 Corresponding to the
Attachment is Operated

[0071] If the control pedal 7c of the control pedal device 7 is operated,
its operation pilot pressure is led via the pilot line 7d to the shuttle
valve 21b of the shuttle valve group 21. The maximum pressure among the
operation pilot pressures including the operation signals from the other
operating units is extracted by the shuttle valve group 21. In this case,
the operation pilot pressure led from the shuttle valve group 21 to the
capacity control system 9 is limited by the solenoid proportional valve
13 in accordance with the operation amount of the control pedal 7c. In
other words, the capacity of the second hydraulic pump 3 is controlled so
that the amount of the hydraulic fluid fed to the corresponding actuators
via the flow control valves B1 to B5 of the second valve group 5b is
limited. Therefore, even if the attachment (the breaker 110 in the
embodiment) is mounted to the front work device 103 and work is intended
to be done, the delivery rate of the second hydraulic pump 3 is not
increased in accordance with the operation of the control pedal 7c of the
control pedal device 7. Thus, the hydraulic fluid at a flow rate
necessary for the attachment is not supplied to thereby significantly
lower the working speed, so that the work using the attachment cannot be
done.

(1-3) In the Case where the Operating Unit Corresponding to the Front
Work Device 103 and the Control Pedal Device 7 Corresponding to the
Attachment are Concurrently Operated

[0072] The operating units (not shown) of the actuators corresponding to
the flow control valves B1 to B5 of the second valve group 5b and the
control pedal 7c of the control pedal device 7 may concurrently be
operated. In such a case, as described in above-mentioned (1-2), the
operation pilot pressure led from the shuttle valve group 21 to the
capacity control system 9 is limited by the solenoid proportional valve
13 in accordance with the operation amount of the control pedal 7c. In
other words, the capacity of the second hydraulic pump 3 is controlled,
so that the amount of the hydraulic fluid supplied to the corresponding
actuators via the flow control valves B1 to B5 of the second valve group
5b is limited. Therefore, even if the attachment (the breaker 110 in the
embodiment) is mounted on the front work device 103 and work is intended
to be done, the delivery rate of the second hydraulic pump 3 is not
increased in accordance with the operation of the control pedal 7c of the
control pedal device 7 and with the operation of the operating unit
corresponding to the front work device 103. Thus, hydraulic fluid at a
flow rate necessary for the actuators of the attachment and of the front
work device 103 is not supplied to thereby significantly lower the
working speed, so that the work cannot be done.

(2) At the Time of Selecting the Attachment Mode

[0073] If the attachment selection device 20 selects the attachment mode
(e.g. the ATT1 mode in which the breaker 110 is used as the attachment),
the pump upper-limit flow selection switch section 72 is switched to the
ATT1 pump upper-limit flow setting section 71b. In addition, the
operation mode selection switch portion 77 is switched to the ATT mode
side. The proportional valve pressure calculation section 78 calculates
proportional valve pressure by use of the pump upper-limit capacity
selected by the maximum value selection section 75. The pump proportional
valve output calculated by the proportional valve output current
calculation section 79 using the proportional valve pressure becomes the
output of the control unit 12. Additionally, the attachment selection
switch section 82 is switched to the solenoid valve OFF-setting section
80 side, so that the solenoid directional control valve output adapted to
OFF-control the solenoid directional control valve 14 becomes the output
of the control unit 12. If the solenoid directional control valve 14 is
OFF-controlled, the pilot line 14a is at a delivery pressure of the pilot
pump 4. In addition, the directional control valve 15 is switched to the
left position shown in the figure so that the hydraulic line 62a of the
second actuator line 62 communicates with the tank T.

(2-1) In the Case where the Operating Unit Corresponding to the Front
Work Device 103 is Operated

[0074] If the operating units (not shown) of the actuators corresponding
to the flow control valves B1 to B5 of the second valve group 5b are
operated, the maximum pressure among their operation signals (the
operation pilot pressures) is extracted by the shuttle valve group 21 and
led to the capacity control system 9. The capacity control system 9
controls the capacity of the second hydraulic pump 3 on the basis of such
a pilot pressure. In other words, the capacity of the second hydraulic
pump 3 is controlled so that the amount of fluid necessary to be supplied
to the corresponding actuators via the flow control valves B1 to B5 of
the second valve group 5b is delivered. In this way, the bucket is
mounted on the front work device 103 and excavating can be done.

(2-2) In the Case where the Control Pedal Device 7 Corresponding to the
Attachment is Operated

[0075] If the control pedal 7c of the control pedal device 7 is operated,
its operation pilot pressure is led via the pilot line 7d to the shuttle
valve 21b of the shuttle valve group 21. The maximum pressure among the
operation pilot pressures including the operation signals from the other
operating units is extracted by the shuttle valve group 21. In this case,
the operation pilot pressure led from the shuttle valve group 21 to the
capacity control system 9 is limited by the solenoid proportional valve
13 so as to provide the pump upper-limit flow rate corresponding to the
attachment mode (ATT1) selected by the attachment selection device 20. In
short, the pump upper-limit capacity of the capacity of the second
hydraulic pump 3 is controlled to a value suitable for ATT1. Thus, the
attachment (the breaker 110 in the present embodiment) can be mounted on
the front work device 103 and the work can be done. In addition, the
attachment is not used with its specifications exceeded so that it is
possible to suppress the occurrence of the failure and reduced life of
the attachment and of the other hydraulic devices.

(2-3) In the Case where the Operating Unit Corresponding to The Front
Work Device 103 and the Control Pedal Device 7 Corresponding to the
Attachment are Concurrently Operated

[0076] The operating unit (not shown) of the actuators corresponding to
the flow control valves B1 to B5 of the second valve group 5b, and the
control pedal 7c of the control pedal device 7 may concurrently be
operated. In such a case, as described in the above (2-2), the operation
pilot pressure led from the shuttle valve group 21 to the capacity
control system 9 is limited by the solenoid proportional valve 13 so as
to provide the pump upper-limit flow rate corresponding to the attachment
mode (ATT1) selected by the attachment selection device 20. In short, the
pump upper-limit capacity of the capacity of the second hydraulic pump 3
is controlled to a value suitable for ATT1. Thus, the attachment (the
breaker 110 in the present embodiment) is mounted on the front work
device 103 and the work can be performed while operating the front work
device 103. In addition, the attachment is not used with its
specifications exceeded so that it is possible to suppress the occurrence
of the failure and reduced life of the attachment and of the other
hydraulic devices.

[0077] In the embodiment configured as described above, if the pedal 7c of
the control pedal device 7 is operated with the non-attachment mode
selected in the attachment selection device 20, the flow rate of the
hydraulic fluid to be supplied to the attachment is limited by limiting
the delivery rate of the second hydraulic pump 3. In the case where the
attachment is mounted on the front work device 103 and various works are
to be done, the attachment may be operated still in the non-attachment
mode where the setting corresponding to the type of the attachment is not
made. In such a case, therefore, the working speed of the attachment is
significantly lowered, so that the work cannot be done. Thus, it is
possible to suppress the failure and reduced life of the attachment and
of the other hydraulic devices in the event that an operator has
forgotten to switch from the non-attachment mode to the attachment mode
and has operated the attachment.

[0078] Additionally, it is possible to allow the operator to recognize
that she or he has forgotten to switch from the non-attachment mode to
the attachment mode. Prompting the operator to switch the operation mode
to the attachment mode can further surely suppress the failure and
reduced life of the attachment and of the other hydraulic devices.

Second Embodiment

[0079] A second embodiment of the present invention is described with
reference to FIGS. 6 to 9. FIG. 6 schematically illustrates the entire
configuration of a hydraulic circuit system for a hydraulic excavator
provided with an attachment control apparatus according to the present
embodiment. FIG. 7 is a block diagram illustrating processing contents of
a control unit according to the present embodiment. FIG. 8 illustrates
the details of processing contents of a pump capacity control section.
FIG. 9 illustrates the details of processing contents of a pilot pressure
control section. Incidentally, FIGS. 7 to 9 concurrently illustrate the
attachment selection device 20 for explanation. In the figures, the
configurations equivalent to those shown in FIGS. 1 to 5 are denoted with
like reference numerals and their explanations are omitted.

[0080] Referring to FIG. 6, similarly to the first embodiment, the
hydraulic circuit system for the hydraulic excavator according to the
present embodiment includes a prime mover 1 such as an engine; two main
pumps, i.e., variable displacement first and second hydraulic pumps 2 and
3 driven by the prime mover 1; a fixed displacement pilot pump 4 driven
by the prime mover 1; a control valve unit 5 connected to the first and
second hydraulic pumps 2, 3; a breaker 110 as an attachment connected to
the control valve unit 5; a plurality of hydraulic actuators including a
boom cylinder 111, an arm cylinder 112, a bucket cylinder 113 and a swing
motor 107 which are connected to the control valve unit 5 and not shown
in the figure; a control pedal device 7 (attachment operating means) for
operating the attachment (the breaker 110 in the embodiment); a plurality
of operating units (not shown) including the operating units (not shown)
for operating hydraulic actuators such as the boom cylinder 111, the arm
cylinder 112, the bucket cylinder 113, the swing motor 107, traveling
motors 114a, 114b, etc.; and pump capacity control systems 8, 9 for
controlling the capacities (displacement volume or tilting of a swash
plate) of the first and second hydraulic pumps 2, 3.

[0081] An attachment control apparatus according to the present embodiment
is installed in the hydraulic circuit system for the hydraulic excavator
as described above. The attachment control apparatus includes an
attachment selection device 20 (mode switching means), an operation
amount sensor 7e installed in the control pedal device 7, a solenoid
proportional valve 13, a solenoid directional control valve 14, a
directional control valve 15, solenoid proportional valves 200, 201, and
a control unit 212.

[0082] The solenoid proportional valves 200 and 201 are installed on the
pilot lines 7a and 7b, respectively, adapted to output operation pilot
pressure from the control pedal device 7 to a flow control valve B4 for
an actuator. In addition, the solenoid proportional valves 200 and 201
are controlled according to the current flowing from the control unit 212
to solenoids 200a and 201a, respectively. If current flowing in the
solenoid 200a is equal to 0, that is, if the solenoid directional control
valve 200 is not energized, the solenoid directional control valve 200 is
switched by the force of a spring 200b to a position (OFF-position) to
lead the operation pilot pressure from the control pedal device 7 to a
pressure-receiving portion 51a of the flow control valve B4. If exciting
current flows in the solenoid 200a, the solenoid directional control
valve 200 is switched to a position (ON-position) to lead the tank
pressure to the pressure-receiving portion 51a of the flow control valve
B4. Similarly, if current flowing in the solenoid 201a is equal to 0,
that is, if the solenoid directional control valve 201 is not energized,
the solenoid directional control valve 201 is switched by the force of a
spring 201b to a position (OFF-position) to lead the operation pilot
pressure from the control pedal device 7 to a pressure-receiving portion
51b of the flow control valve B4. If exciting current flows in the
solenoid 201a, the solenoid directional control valve 201 is switched to
a position (ON-position) to lead tank pressure to the pressure-receiving
portion 51b of the flow control valve B4.

[0083] The control unit 212 is adapted to control the attachment control
apparatus according to the present embodiment. The control unit 212
outputs a drive current to the solenoid proportional valve 13 and the
solenoid directional control valves 14, 200, 201 on the basis of the
input from the attachment selection device 20 and the operation amount
sensor 7e.

[0084] Referring to FIG. 7, the control unit (C/U) 212 includes a capacity
control section 212A (see FIG. 8), a hydraulic line control section 12B
and a pilot pressure control section 212C. The capacity control section
212A controls the capacity of the second hydraulic pump 3 by controlling
the solenoid proportional valve 13 on the basis of the selection result
of the attachment selection device 20 and the detection result of the
operation amount sensor 7e of the control pedal device 7. The hydraulic
line control section 12B switches between the positions of the
directional control valve 15 by controlling the solenoid directional
control valve 14 on the basis of the selection result of the attachment
selection device 20. The pilot pressure control section 212C controls the
solenoid directional control valves 200, 201 on the basis of the
selection result of the attachment selection device 20.

[0086] The pump upper-limit capacity second calculation section 276
receives the detection result of the operation amount (the ATT operation
amount) of the control pedal 7c from the operation amount sensor 7e of
the control pedal device 7. In addition, the pump upper-limit capacity
second calculation section 276 refers the detection result to a table
stored in a memory and calculates the pump upper-limit capacity
corresponding to the then ATT operation amount. On the table of the
memory, the relationship between the ATT operation amount and the pump
upper-limit capacity is established so that the pump upper-limit capacity
may be constant (e.g. the maximum delivery capacity of the second
hydraulic pump 3) regardless of the ATT operation amount.

[0087] Referring to FIG. 9, the pilot pressure control section 212C has a
function of each of a solenoid valve OFF-setting section 90, a solenoid
valve ON-setting section 91 and an attachment selection switch section
92.

[0088] The solenoid valve OFF-setting section 90 has a function of
outputting a current (current 0 (zero)) adapted to switch the solenoid
valves 200, 201 to an OFF-position. The solenoid valve ON-setting section
91 has a function of outputting a current adapted to switch the solenoid
valves 200, 201 to an ON-position, i.e., a current adapted to excite the
respective solenoids 200a, 201a of the solenoid valves 200, 201 and
switch the valves 200, 201 to the ON-position.

[0089] If the attachment selection device 20 selects the mode in which the
attachment is used (the attachment mode: ATT1 to ATT8), the attachment
selection switch section 92 is switched to the ATT mode side (i.e., the
solenoid valve OFF-setting section 90 side). The attachment selection
switch section 92 outputs the current adapted to OFF-control (to switch
to the OFF-position) the solenoid valves 200, 201 as an output of the
attachment control section 212C. If the attachment selection device 20
selects the mode in which excavation is performed by use of the bucket
(non-attachment mode: excavation), the attachment selection switch
section 92 is switched to the side except the ATT mode (i.e., the
solenoid valve ON-setting section 91 side). In addition, the attachment
selection switch section 92 outputs the current adapted to ON-control (to
switch to the ON-position) the solenoid valves 200, 201 as an output of
the attachment control section 212C.

[0090] The other configurations are the same as those of the first
embodiment.

[0091] A description is given of the operation of the embodiment
configured as described above.

(1) At the Time of Selecting the Non-Attachment Mode

[0092] If the attachment selection device 20 selects the excavation mode
(the non-attachment mode), the pump upper-limit flow selection switch
section 72 is switched to one (e.g. the ATT1 pump upper-limit flow rate
71b) of the pump upper-limit flow setting section group 71. In addition,
the operation mode selection switch section 77 is switched to the side
except the ATT mode. The proportional valve pressure calculation section
78 calculates proportional valve pressure by use of the pump upper-limit
capacity calculated by the pump upper-limit capacity second calculation
section 76. The pump proportional valve output calculated in the
proportional valve output current calculation section 79 by use of the
proportional valve pressure becomes the output of the control unit 12.
Additionally, the attachment selection switch section 82 is switched to
the solenoid valve ON-setting section 81 side. The solenoid directional
control valve output adapted to ON-control the solenoid directional
control valve 14 becomes the output of the control unit 12. If the
solenoid directional control valve 14 is ON-controlled, the pilot line
14a is at a tank pressure. The directional control valve 15 is switched
to the right position shown in the figure to allow the hydraulic lines
62a, 62b of the second actuator line 62 to communicate with each other.
The attachment selection switch section 92 is switched to the solenoid
valve ON-setting section 91 side, so that the solenoid directional
control valve output adapted to ON-control the solenoid directional
control valves 200, 201 becomes the output of the control unit 212. If
the solenoid directional control valves 200, 201 are ON-controlled, the
pilot lines 7a, 7b to which the operation pilot pressure of the control
pedal device 7 is outputted are blocked. Thus, the tank pressure is led
to the pressure-receiving portions 51a, 51b of the flow control valve B4.

(1-1) In the Case where the Operating Unit Corresponding to the Front
Work Device 103 is Operated

[0093] If the operating units (not shown) of the actuators corresponding
to the flow control valves B1 to B5 of the second valve group 5b are
operated, the maximum pressure among their operation signals (the
operation pilot pressures) is extracted by the shuttle valve group 21 and
led to the capacity control system 9. The capacity control system 9
controls the capacity of the second hydraulic pump 3 on the basis of such
a pilot pressure. In other words, the capacity of the second hydraulic
pump 3 is controlled so that the amount of fluid necessary to be supplied
to the corresponding actuators via the flow control valves B1 to B5 of
the second valve group 5b is delivered. Thus, the bucket is mounded on
the front work device 103 and excavating can be done.

(1-2) In the Case where the Control Pedal Device 7 Corresponding to the
Attachment is Operated

[0094] If the control pedal 7c of the control pedal device 7 is operated,
the operation pilot pressure is outputted to the pilot lines 7a, 7b.
However, the operation pilot pressure is blocked by the solenoid
directional control valves 200, 201, so that the flow control valve B4 is
not switched from a neutral position. Therefore, even if work is intended
to be performed by mounting the attachment (the breaker 110 in the
present embodiment) on the front work device 103, since the hydraulic
fluid is not supplied to the attachment, the work using the attachment
cannot be done. The control is executed in which the pilot pressure to be
outputted to the pilot line 7d is selected by the shuttle valve group 21
and supplied to the capacity control system 9 to increase the capacity of
the second hydraulic pump 3. However, since the flow control valves B1 to
B5 are not switched, the second hydraulic pump 3 is under no-load
running.

(1-3) In the Case where the Operating Unit Corresponding to the Front
Work Device 103 and the Control Pedal Device 7 Corresponding to the
Attachment are Concurrently Operated

[0095] In this case, as with the above (1-1), if the operating units (not
shown) of the actuators corresponding to the flow control valves B1 to B5
of the second valve group 5b are operated, the maximum pressure among
their operation signals (the operation pilot pressures) is extracted by
the shuttle valve group 21 and led to the capacity control system 9. The
capacity control system 9 controls the capacity of the second hydraulic
pump 3 on the basis of such a pilot pressure. In other words, the
capacity of the second hydraulic pump 3 is controlled so that the amount
of fluid necessary to be supplied to the corresponding actuators via the
flow control valves B1 to B5 of the second valve group 5b is delivered.
Thus, the bucket is mounded on the front work device 103 and excavating
can be done. Additionally, as illustrated in the above (1-2), if the
control pedal 7c of the control pedal device 7 is operated, the operation
pilot pressure is outputted to the pilot lines 7a, 7b. However, the
operation pilot pressure is blocked by the solenoid directional control
valves 200, 201, so that the flow control valve B4 is not switched from a
neutral position. Therefore, even if work is intended to be done by
mounting the attachment (the breaker 110 in the present embodiment) on
the front work device 103, since the hydraulic fluid is not supplied to
the attachment, the work using the attachment cannot be done.

(2) At the Time of Selecting the Attachment Mode

[0096] If the attachment selection device 20 selects the attachment mode
(e.g. the ATT1 in which the breaker 110 is used as the attachment), the
pump upper-limit flow selection switch section 72 is switched to the ATT1
pump upper-limit flow rate 71b. In addition, the operation mode selection
switch section 77 is switched to the ATT mode side. Proportional valve
pressure is calculated by the proportional valve pressure calculation
section 78 by use of the pump upper-limit capacity selected by the
maximum value selection section 75. The pump proportional valve output
calculated by the proportional valve output current calculation section
79 by use of the proportional valve pressure becomes the output of the
control unit 212. Additionally, the attachment selection switch section
82 is switched to the solenoid valve ON-setting section 81 side, so that
the solenoid directional control valve output adapted to OFF-control the
solenoid directional control valve 14 becomes the output of the control
unit 212. If the solenoid directional control valve 14 is OFF-controlled,
the pilot line 14a is at a delivery pressure of the pilot pump 4. In
addition, the directional control valve 15 is switched to the left
position shown in the figure so that the hydraulic line 62a of the second
actuator line 62 communicates with the tank T. Additionally, the
attachment selection switch section 92 is switched to the solenoid valve
OFF-setting section 90 side, so that the solenoid directional control
valve output adapted to OFF-control the solenoid directional control
valves 200, 201 becomes the output of the control unit 212. If the
solenoid directional control valves 200, 201 are OFF-controlled, the
operation pilot pressure of the control pedal device 7 is led to the
pressure-receiving portions 51a and 51b of the flow control valve B4 via
the pilot lines 7a and 7b, respectively.

(2-1) In the Case where the Operating Unit Corresponding to the Front
Work Device 103 is Operated

[0097] If the operating units (not shown) of the actuators corresponding
to the flow control valves B1 to B5 of the second valve group 5b are
operated, the maximum pressure among their operation signals (the
operation pilot pressures) is extracted by the shuttle valve group 21 and
led to the capacity control system 9. The capacity control system 9
controls the capacity of the second hydraulic pump 3 on the basis of such
a pilot pressure. In other words, the capacity of the second hydraulic
pump 3 is controlled so that the amount of fluid necessary to be supplied
to the corresponding actuators via the flow control valves B1 to B5 of
the second valve group 5b is delivered. Thus, the bucket is mounded on
the front work device 103 and excavating can be done.

(2-2) In the Case where the Control Pedal Device 7 Corresponding to the
Attachment is Operated

[0098] If the control pedal 7c of the control pedal device 7 is operated,
its operation pilot pressure is led via the pilot line 7d to the shuttle
valve 21b of the shuttle valve group 21. The maximum pressure among the
operation pilot pressures including the operation signals from the other
operating units is extracted by the shuttle valve group 21. In this case,
the operation pilot pressure led from the shuttle valve group 21 to the
capacity control system 9 is limited by the solenoid proportional valve
13 so as to provide the pump upper-limit flow rate corresponding to the
attachment mode (ATT1) selected by the attachment selection device 20. In
other words, the pump upper-limit capacity of the capacity of the second
hydraulic pump 3 is controlled to a value suitable for ATT1. Thus, the
attachment (the breaker 110 in the present embodiment) can be mounted on
the front work device 103 and work can be done. In addition, the
attachment is not used with its specifications exceeded so that it is
possible to suppress the occurrence of the failure and reduced life of
the attachment and of the other hydraulic devices.

(2-3) In the Case where the Operating Unit Corresponding to The Front
Work Device 103 and the Control Pedal Device 7 Corresponding to the
Attachment are Concurrently Operated

[0099] The operating units (not shown) of the actuators corresponding to
the flow control valves B1 to B5 of the second valve group 5b and the
control pedal 7c of the control pedal device 7 may concurrently be
operated. In such a case, as described in the above (2-2), the operation
pilot pressure led from the shuttle valve group 21 to the capacity
control system 9 is limited by the solenoid proportional valve 13 so as
to provide the pump upper-limit flow rate corresponding to the attachment
mode (ATT1) selected by the attachment selection device 20. In short, the
pump upper-limit capacity of the capacity of the second hydraulic pump 3
is controlled to a value suitable for ATT1. Thus, the attachment (the
breaker 110 in the present embodiment) is mounted on the front work
device 103 and work can be performed while operating the front work
device 103. In addition, the attachment is not used with its
specifications exceeded so that it is possible to suppress the occurrence
of the failure and reduced life of the attachment and of the other
hydraulic devices.

[0100] In the present embodiment configured as described above, in the
state where the non-attachment mode is selected by the attachment
selection device 20, the control pedal 7c of the control pedal device 7
may be operated. Even in such a case, the operation signal (the operation
pilot pressure) transmitted from the control pedal device 7 to the
attachment flow control valve B4 is blocked by the solenoid directional
control valves 200, 201. In the case where the attachment is mounted on
the front work device 103 and various works are to be performed, the
attachment may be operated with the non-attachment mode remaining
selected without setting corresponding to the type of the attachment.
Even in such a case, therefore, the drive fluid is not supplied to the
attachment via the flow control valve B4. Thus, it is possible to prevent
the failure and reduced life of the attachment and of the other hydraulic
devices in the event that an operator has forgotten to switch from the
non-attachment mode to the attachment mode and has operated the
attachment.

[0101] Additionally, it is possible to allow the operator to recognize
that she or he has forgotten to switch from the non-attachment mode to
the attachment mode. Prompting the operator to switch the operation mode
to the attachment mode can further surely suppress the failure and
reduced life of the attachment and of the other hydraulic devices.